The rows, columns and two long diagonals in this chart all add up to 34.

Now let's suppose that you are forbidden to use the numbers 2 and 15, but allowed in their place to repeat any two numbers already in use, how would you construct your square so that rows, columns and diagonals should still add up to 34?

Your ability to achieve this will depend on the two numbers that you select to replace 2 and 15